Jim replaced the emitter and changed the shields
I coated with 0.5 micron Al.
Gun was a little unstable at first, but fairly quickly became normal.
One problem observed, unrelated to new gun:
When I tunred on the planetary rotation, the PS tripped
off, gate valve closed, pressure shot up, and cryo temp
went up to 22K.
This appeared to be a real pressure burst. I restarted,
and everything was eventually ok, but pressure and
cryo temp were slow to recover (5 min or so).